1. Field of the Invention
This invention relates to a dispenser for creamy substances such as creams for cosmetic use, of the type comprising a container bounding a cylindrical chamber containing the creamy substance and closed at one end by a piston movable in a sealed manner along said chamber.
2. Description of the Related Art
Many known types of dispensers are provided with mechanical devices for moving the piston only in that direction which reduces the volume of the chamber containing the creamy substance. Reference can be made for example to U.S. Pat. No. 421,255, EP-A-0051790, EP-A-0084638, U.S. Pat. No. 3,088,636 and U.S. Pat. No. 3,768,705. These dispensers have a relatively complex structure, are costly and their operation is often difficult and unsatisfactory.
Dispensers are also known having two separate chambers mutually communicating via a non-return valve. Of the two chambers, one is cylindrical and is intended only to act as a container for the creamy substance, it being closed at one end by a sealed piston freely slidable within the chamber. The other chamber is the dispensing chamber and is at least partially deformable (to allow compression of that part of the substance contained in it and drawn by suction from the cylindrical chamber via a non-return valve). It comprising a dispensing nozzle provided with a closure element to allow the substance to pass only to the outside.
When dispensing ceases, the deformable part of the dispensing chamber returns to its rest position to close the nozzle and generate a vacuum which draws the substance from the cylindrical chamber to the dispensing chamber via the non-return valve.
These types of dispensers (described for example in U.S. Pat. No. 4,821,926, U.S. Pat. No. 4,890,773, U.S. Pat. No. 4,913,322, U.S. Pat. No. 4,946,076, U.S. Pat. No. 5,176,291 and EP-A-0 686 431) have a rather complex mechanical structure with rigid component parts slidable one on another, causing considerable operating problems as a result of the possible hardening of the creamy substances within the respective dispensing chambers, difficult assembly and consequent relatively high cost.
To overcome the aforementioned problems, improvements have been proposed to the dispensers of the latter type, by forming with elastically deformable material an entire wall bounding the dispensing chamber. By squeezing and deforming this wall, the cream contained in this chamber is directly compressed, so that it emerges through the discharge nozzle.
A series of dispensers of this type are illustrated in EP-A-0376097, but these dispensers have a very complex structure, requiring, inter alia, the presence and operation of levers for squeezing the deformable wall of the dispensing chamber.
A simpler and more economical version of the dispenser having a dispensing chamber bounded by an elastically deformable wall is represented in U.S. Pat. No. 5,377,880 (and in the corresponding European patent EP-A-0600286) in which the dispensing nozzle consists of a hole provided in the deformable wall. This hole is positioned in correspondence with the free end of a rigid peg fixed to project into the dispensing chamber. When in the rest state, the deformable wall is elastically urged towards the peg such that the end of the peg is reliably forced into the hole to seal it. As this sealing depends only on the elastic compression force (which necessarily cannot be high) developed by the elastic wall on the end of the pin, and as the dispensing chamber is filled with creamy substance which tends to urge the elastic wall outwards, it follows that the sealing of the dispensing chamber is very uncertain. Moreover, as the cream is dispensed to the outside only when the orifice defining the discharge hole is deformed elastically such that only a small portion of the surface of this hole is withdrawn from the adjacent surface of the peg, it follows that, to be dispensed to the outside, the cream must pass through a very small aperture (because most of the hole remains obstructed by the end of the pin), and hence dispensing is difficult and very slow.